Methods such as these are known and are used for door drives, for example for elevator doors. Where the expression door is used in the following text, then this always covers any type of doors or gates without this being expressly mentioned in the text. Methods of this generic type are used in order to ensure, particularly when the door is being closed, that people located in the closing area are not injured and/or objects are not damaged. The drives are therefore controlled such that, if the door is blocked or obstructed by an obstruction, the drive motor or motors is or are stopped in good time so that there is no risk of injury and damage.
It is known, for example from DE 196 28 238 C2, for the door drive to be rendered inoperative via a so-called force switch-off. For this purpose, the closing force required to close the door is measured over the closing movement, and is stored, during a measurement run. The closing force is normally measured by determining the torque required by the electrical door drive motor during at least one measurement process at a defined closing rate, so that the force profile and the speed profile of the door can be determined during the closing and opening movements, from the measured values. The closing torque required to close the door and the maximum permissible closing torque can be determined from the measured values at every point during the closing movement of the door and, if these are exceeded, during operation, this leads to the door drive motor being switched off.
For understandable reasons, there is an aim to keep the response times of the door drive motor switch-off as short as possible in order to reduce the closing force immediately to zero if the door is blocked, and possibly to initiate reversal of the door closing movement. The door movement processes do not take place at a uniform speed, and in fact acceleration and braking processes are the rule at the start and at the end of the closing and opening movements.
The speed profile while the door is being closed can likewise be determined with the aid of measurement runs, and can be read into the memory for the door control system. Discrepancies from the stored speed profile during door operation may be an indication of a disturbance, for example blocking of the door closing movement.
Adaptation of the motor torque (current consumption) and speed of the closing movement can in this case provide more accurate results than simple monitoring of the closing force of the door, and can therefore ensure that normal fluctuations in the motor torque, for example in the event of the door guides becoming dirty, are identified and taken into account without this immediately leading to the drive being switched off.
Since door control systems of the described type always present a considerable risk, in particular to people who are located in the closing area of the door, in the event of malfunctions when obstruction blocking occurs, the aim is to ensure that, in the event of a functional failure of the safety control system, of whatever type, a redundant system is provided to reliably prevent injuries and damage to people and objects.